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Density of Materials

• Density = measure of compactness of a substance. It relates the mass of a substance to how much space it can take up
• Density (kg/m³) = mass(kg) / volume(m³)
• Density depends on what the material is made of and particle arrangement
• Dense material = particles are packed tightly together
• Less dense material = particles are more spread out. If you compressed the material = particles would move closer together = more dense = decreasing volume, but mass remains the same
• Three states of matter: solids, liquids and gases.
• 1. Solids: strong forces of attraction hold the particles closely in a fixed and regular arrangement . As particles don’t have much energy they can only vibrate about their fixed positions.Highest density = as particles are closest

2. Liquids: weaker forces of attraction between particles. Particles are close but can move past each other and form irregular arrangements. Particles have more energy than in a solid so move in random direction at low speed. Liquids less dense than solids usually.

3. Gases: almost no forces of attraction between the particles. Particles have the most energy, so they are free to move and travel in random directions at high speeds. They have low densities

• PRACTICAL: measure density in different ways
• Density of a solid object:
• 1. Use a balance to measure mass

2. If it’s a regular solid, measure its length, width and height. Calculate volume

3. If it’s an irregular solid, find the volume by submerging it in a eureka can filled with water. The water displaced by the object will be transferred to the measuring cylinder.

4. Record volume of water in the measuring cylinder = volume of the object

5. Find density using the formula: density = mass/volume

• Density of a liquid:
• 1. Place a measuring cylinder on a balance and zero it

2. Pour 10ml of the liquid into the cylinder and record the mass of the liquid

3. Pour another 10ml into the measuring cylinder. Repeat this process until the cylinder is full and record the total volume and mass each time

4. For each measurement, use d=m/v to find the density. (1ml=1cm³)

5. Take an average of all the calculated densities

How long have you…? (present perfect 4) Exercises

Use the information given to create questions beginning with ‘How long…?’

• It is snowing.

• The weather is shining.

• John and Kate are married.

• My brother has gone on holiday.

• My aunty and uncle live in Canada.

• My sister is a teacher.

• I work at the chemist.

• I’ve known Susan since I was a baby.

• Jonathan is learning to speak to Mandarin.

Fill in the missing gaps in the sentences using the present perfect (=has/have + past participle)

• I have known Kate a long time.

• My brother has been playing the piano he was 11 years old.

• My mum and dad on holiday to America. They

gone since last Sunday.

• I Ben and Emma since primary school.

We to the same primary and secondary school.

• My sister learning to speak French because she
is going to France next month.

Use the appropriate words in the missing gaps.

have you lived       lives      to

has been       works        have known

I have bought       have worked.

• My sister in Spain. She is studying Spanish

with her friend Rosie. I Rosie since I was 5.

• Spencer like with Jamie. They have worked

together for 2 years.

• How long in Australia?

• a new dress for prom.

• He to Thorpe park.

Challenge: Create 4 of your own questions beginning with ‘How long……?’

1.

2.

3.

4.

1 2 3 4 5 6

“Every accomplishment starts
With the decision to try.” Gail Dever

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