Grade 8 Science Unit 1: Mix and Flow of Matter

Observing Fluid Flow

• To observe a gas flowing, use its effect, as gases cannot be seen or heard.
• Characteristics of fluids include their effect, hearing, seeing, and feeling.

Properties of Substances

• Properties of substances can be classified into two categories: physical properties and properties of behavior.
• Physical properties include color, density, and crystal size.
• Properties of behavior include whether a substance burns, rots, or explodes, and its reactivity.

Chemical Properties

• Chemical properties include reactivity, acidity, and solubility.
• Chlorine is useful because of its reactivity.

States of Matter

• Substances can exist in different states, such as hydrated (with water) or anhydrous (without water).
• Copper II Sulphate can be hydrated or anhydrous.

Mixtures

• A mixture is a combination of two or more substances that can be separated by physical means.
• To determine if a substance is a mixture, look for the number of parts visible.
• Mortar is a mixture of sand and cement, and its effectiveness depends on proper proportions.

Pure Substances

• To determine if a substance is pure, look for its density, color, and boiling point in a standard reference table.
• Certain substances decompose when heated, which can affect their boiling point.

Fluid Flow

• The flow rate of a fluid depends on its viscosity and temperature.
• Increasing the temperature of a fluid can decrease its viscosity, making it flow faster.
• Windshield washer fluid is a solution that needs to be designed for winter conditions, considering its melting point.

Drag and Viscosity

• The drag exerted on objects moving through air is caused by air molecules colliding with the object.
• The shape of an object affects the drag it experiences, with some shapes experiencing more drag than others.
• Viscosity is the measure of a fluid's resistance to flow, and it can be affected by temperature and pressure.

Buoyancy

• Buoyancy is the upward force exerted on an object by a fluid, such as water or air.
• The buoyant force depends on the density of the fluid and the volume of the object.
• Objects experience less weight when submerged in a fluid due to the buoyant force.

Density and Buoyancy

• Density is the mass of a substance per unit volume.
• The density of a fluid affects the buoyant force it exerts on an object.
• As the density of a fluid increases, the buoyant force increases.

Applications

• Snowshoes make it easier to walk on snow by spreading out the force over a larger area, reducing the pressure on the ground.
• Wider, thicker tires on mountain bikes or all-terrain vehicles offer better traction or grip on the terrain.
• The water pressure at a depth of 1 m below the water surface in a swimming pool is 10 000 Pa.

Test your understanding of the mix and flow of matter with this quiz, covering physical properties, behavior, and characteristics of fluids and gases. Suitable for Grade 8 students.